Directional control for rock drill feed support

ABSTRACT

A direction sensing unit and control circuit for prepositioning a rock drill feed support to provide for drilling a series of parallel holes. The direction sensing unit is mounted on the feed support and includes a pivotally mounted weight responsive to gravitational force acting thereon to actuate a plurality of pneumatic valves to provide pressure signals. The control circuit includes pneumatically operated control valves which, in response to receiving pneumatic pressure signals from the sensing unit, are operable to valve hydraulic fluid to and from hydraulic positioning cylinders connected to the feed support.

States te Hanson 1March 20, 1973 DIRECTIONAL CONTROL FOR ROCK DRILL FEEDSUPPORT [75] inventor: Laurence B. Hanson, Pine, Colo.

[73] Assignee: Gardner-Denver, Quincy, Ill.

[22] Filed: May 4, 1971 [21] Appl. No.: 140,142

[52] U.S. Cl ..173/2, 173/43 [51] Int. Cl ..E21c 11/02 [58] Field ofSearch ..173/2, 38, 43; 91/419; 182/2 [56] References Cited UNITEDSTATES PATENTS 3,481,409 12/1969 Westerlund ..l73/43 2,520,266 8/1950Adams ....9l/419 X 3,437,010 4/1969 Jacobi et al ..91/419 X PrimaryExaminer-Ernest R. Purser Attorney-Micheal E. Martin [5 7 ABSTRACT Adirection sensing unit and control circuit for prepositioning a rockdrill feed support to provide for drilling a series of parallel holes.The direction sensing unit is mounted on the feed support and includes apivotally mounted weight responsive to gravitational force actingthereon to actuate a plurality of pneumatic valves to provide pressuresignals. The control circuit includes pneumatically operated controlvalves which, in response to receiving pneumatic pressure signals fromthe sensing unit, are operable to valve hydraulic fluid to and fromhydraulic positioning cylinders connected to the feed support.

9 Claims, 11 Drawing Figures DIRECTIONAL CONTROL. FOR ROCK DRILL FEEDSUPPORT BACKGROUND OF THE INVENTION sloped surface which will be stableand therefore safe 1 and maintenance free. To this end a technique knownin the art as presplitting or preshearing has developed wherein a seriesof closely spaced parallel holes are drilled to a predetermined depth inthe plane of the desired surface. These presplit holes are loaded withblasting charges and the resulting blasting operation provides a cleanlysheared cut in the earth having a substantially smooth and fissure freesurface.

In presplit drilling it is particularly important that the closelyspaced blast holes are drilled parallel and in the same plane to assurethat a smooth cleavage is provided upon blasting. Overbreakage and roughsurfaces resulting from misaligned holes are costly in terms of extrarock removal required and the development of fissures in the rocksurface. In the latter case entry of moisture into the fissures resultsin erosion and further breakage of rock due to freezing and thawingprocesses.

Heretofore in the drilling of presplit blast holes with portable rockdrilling apparatus the positioning of the rock drill feed support toprovide parallel coplanar holes has been a time consuming and tediousoperation. Moreover, the accuracy of sighting in the directionalattitude of the rock drill centerline by manually operating the valvescontrolling the feed support positioning motors has been so limited thatonly relatively shallow depths of presplit cleavages could be producedfrom drilling a series of holes. Accordingly, many somewhat deep cuts inthe earth have required repeated cycles of drilling, blasting andexcavating to reach the required depth of cut.

Devices are known in the art of rock drill apparatus which are operableto provide for positioning a drill feed support to drill a pattern ofparallel holes. Examples of such devices are disclosed in U.S. Pat. Nos.3,374,975 to H. Bronder, and 3,481,409 to B. A. Westerlund. Whereas theparallel positioning systems disclosed in the above mentioned patentsare suitable for use with a particular type of drilling apparatus fordrilling a pattern of holes in a tunnel face or the like they are notreadily adaptable to be used with conventional mobile drilling apparatushaving elongated drill feed supports which are connected to a support bymeans of a connection providing for pivotal movement I about two axes.

Moreover, prior art directional control systems for rock drill feedsupports are subject to error, or example, due to leakage of hydraulicfluid from series connected positioning motors or wear in the mechanicallinkage connections for certain types of parallel motion mechanisms.

SUMMARY OF THE INVENTION The present invention provides for portablerock drilling apparatus including a movable feed support automaticallypositionable to provide for drilling a series of parallel blast holes orthe like. With the rock drilling apparatus of the present invention aseries of blast holes may be drilled at a predetermined angle withrespect to a plumb line, said holes being virtually parallel and in apredetermined plane.

More specifically, the present invention provides a directional controlsystem for a rock drill feed support which is operable to provide forsubstantially automatic positioning of the feed support to be properlyaligned for drilling a series of spaced parallel holes such as used forpresplit cleaving of rock faces. With the directional control system ofthe present invention otherwise conventional portable rock drillingapparatus having swingable boom mounted feed supports may be morerapidly and accurately positioned for drilling parallel coplanar holesin the ground.

There is also provided in the present invention a direction sensing unitresponsive to gravitational force to provide pneumatic signals to apressure fluid control circuit which in turn is operable to control aplurality of pressure fluid positioning motors. The completely pressurefluid operated directional control system of the present invention isoperable to utilize pressure fluid normally supplied for use otherwiseon portable rock drilling apparatus.

Although the directional control system of the present invention isdisclosed in combination with a rock drill apparatus used primarily fordrilling on the surface of the earth the directional control system maybe advantageously used with rock drill units suited for undergroundmining and tunneling excavation as well.

With the directional control system of the present invention incombination with a portable rock drill apparatus a series of spacedparallel blast holes may be drilled faster and more accurately alignedthan with heretofore known equipment BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a side elevation of a mobile rock drill rig embodying thedirectional control system of the present invention.

FIG. 2 is a detail plan view of the boom pivot of the rock drill rig ofFIG. 1.

FIG. 3 is an elevation of the directional sensing unit mounting.

FIG. 4 is a plan view of the directional sensing unit mounting. FIG. 5is a plan view of the rock drill rig of FIG. 1 showing the drillingpattern of a series of presplit blast holes.

FIG. 6 is a sketch of a typical cross section of a roadway excavationhaving presplit sloped sides.

FIG. 7 is a center longitudinal section view of the directional sensingunit taken along the line 77 of FIG. 4.

FIG. 8 is a section taken along the line 88 of FIG. 7.

FIG. 9 is a schematic of the directional sensing unit and controlcircuit of the present invention.

FIG. 10 is a detail view of the feed support mounting.

FIG. 11 is a detail taken along the line 11--11 of FIG. 7

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2 amobile rock drill apparatus or rig is illustrated and generallydesignated by the numeral The rock drill rig 10 includes a crawlerundercarriage 12 including a pair of crawler assemblies 14 pivotallyconnected to a frame 16. The frame 16 is adapted to support an elongatedmovable support or boom 18 by means of a bracket 20 which is pivotallyconnected to the frame 16 for movements about a substantially verticalpivot axis 22 and includes a clevis 24 for pivotal attachment of theboom to the bracket 20. The boom 18 is operable to be elevated about thepivot connection 24 by means of a hydraulic cylinder 26 and to be swungabout the pivot axis 22 of the bracket 20 by a hydraulic cylinder 28.

The boom 18 is of a telescopic type already known in the art of rockdrill apparatus and includes a portion 30 which may be extended withrespect to the portion 32. The distal end of the boom portion 30includes a positioner mechanism 34 pivotally connected thereto. Ahydraulic positioning motor in the form of the cylinder 36 is providedfor pivoting the positioner 34 about a first axis 38. The positionercomprises a bracket 40 which is adapted to have mounted thereon anelongated support 42 for reversibly feeding a percussion rock drillmotor 44 therealong. The bracket 40 is pivotally mounted with respect tothe positioner 34 to be pivoted about a second axis 46 which isperpendicular to the first pivot axis 38. Pivotal movement of thebracket 40 with respect to the positioner, about the axis 46, isaccomplished by means of the fluid operated positioning motor 48comprising a hydraulic cylinder attached to the bracket at 50 and havinga piston rod pivotally connected to the positioner at 52, FIG. 10.

The feed support 42 includes a fluid operated feed motor 54 mountedthereon and operable to reversibly feed the drill motor 44 along thefeed support. The drill motor is operable to deliver percussive blows toan elongated drill rod 56 which has a bit 58 attached to one end and ischucked in the drill motor at its opposite end. The drill rod 56 is heldin desired alignment with respect to the feed support by a centralizer60.

The rock drill rig 10 hereinbefore described is of a type generally wellknown in the art of earth drilling apparatus and is adapted to providefor drilling blast holes in a wide range of directions. Such rigs areprovided with fluid operated motors such as the motors 61, FIGS. 1 and5, whereby they may be moved about from one work location to another. Itis conventional to provide such rigs with self contained power plantsfor providing a source of pressure fluid or in the case of the exemplaryrig 10 a portable compressor or pump, not shown, is connected to the rigby suitable, flexible conduits. Conversion of pressure fluid energy frompneumatic to hydraulic form or vice versa may be accomplished bysuitable motor-pump units on board the rig.

Referring to FIGS. 1, 3, 4 and 5, the rock drill rig 10 is adapted toinclude a control system for positioning the feed support 42 to providea predetermined direction of the longitudinal axis of the drill rod 56,FIG. 1. This predetermined direction is defined with respect to areference which, with the directional control system of the presentinvention, comprises a plumb line 64 or a straight line through thegravitational center ofthe earth.

Referring to FIGS. 1, 3 and 4, the directional control system of thepresent invention includes direction sensing means comprising a sensingunit mounted on the feed support 42 and generally designated by thenumeral 66. The sensing unit 66 is characterized by a substantiallyspherically shaped housing 68 which is mounted on a bracket 70 attachedto the feed support and having a hinged portion 72. The hinged portionof the bracket 70 includes a mounting plate 74 attached thereto andcooperable with the plate 76 to movably clamp the sensing unit 66. Theplate 76 is secured to the plate 74 by bolt and nut assemblies 78.

As shown in FIG. 4 and 5 the hinged portion 72 is movable with respectto the feed support 42 in response to the actuation of the double actinghydraulic cylinder 80 having its rod end attached to the plate 74. Theopposite end of the cylinder 80 is pivotally connected to the mountingbracket at 82. The hydraulic cylinder 80 is interconnected to ahydraulic cylinder 84, as shown schematically in FIG. 4, by conduits 86and 88. The hydraulic cylinder 84 is pivotally connected to the frame 16at one end and at its rod end is pivotally connected to the pivotbracket 20 which supports the boom 18, FIG. 2. The cylinders 80 and 84are arranged at their respective locations and interconnected by theconduits 86 and 88 such that displacement of fluid from either end ofthe cylinder 84 in response to pivotal movement of the bracket 20 willresult in fluid being forced into the corresponding end of the cylinder80 to produce equal movement of the cylinder 80 and, accordingly,angular movement of the hinged portion 72 about its pivot substantiallyequal to the angular movement of the boom 18 about the pivot axis 22 ofthe bracket 20. Such arrangements of fluid cylinders are believed to begenerally well known in the art of fluid power servomechanisms and thepurpose of such an arrangement in regard to the directional controlsystem of the present invention is to provide means for controlling theposition of the sensing unit 66 with respect to a reference as will beexplained further herein. The conduits 86 and 88 interconnecting thecylinders 80 and 84 are also flow connected to conduits 90 and 92 whichin turn are connected to a three position normally closed valve 94represented schematically in FIG. 4 in accordance with USA. Standardfluid power symbols. The valve 94 is in communication with a source ofhydraulic fluid, not shown. The valve 94 isoperable to communicatepressure fluid to either end of the cylinder 80 to effect angularpositioning of the hinged portion 72 of the bracket 70 independently ofany movement of the boom pivot bracket 20. In the arrangement of the rig10, as shown in FIGS. 1 and 2, this independent positioning of thebracket portion 72 is possible due to the fact that fluid pressureacting on the cylinder 84 is not sufficient to overcome the holdingforce of the boom swing cylinder 28.

Referring to FIGS. 7, 8 and 11, the sensing unit 66 as previouslystated, includes a spherically shaped housing 68 having a hollowinterior 96 and a threaded portion 98 which is adapted to receive a base100. The base 100 is adapted to include an elongated rectangular tube102 extending downwardly therefrom. The base 100 further includes aplurality of four cylindrical bores 104 spaced equidistant one from theother along first and second centerlines 106 and 108 which intersect atright angles. Situated in the bores 104 are cylindrical seats 110containing ball valve elements 114a, 114b, 1140, and 114d. The ballvalve elements are operable to be seated over the ends of passages 115in the seat elements 110 to prevent fluid flow through the passages intothe hollow interior 96.

The sensing unit 66 also includes means responsive to gravitationalforce comprising a weight 116 pivotally mounted above the valve elements114a, 114b, 1140, and 114d on a pedestal 118 having a substantiallyspherical shape except for the flat surface portion 120. The pedestal issupported in the socket 122 in the base 100, the socket 112 beinglocated at the intersection of the centerlines 106 and 108. The pedestal118 as well as the seat elements 110 are retained on the base 100 by aplate 124 suitably secured to the base by threaded fasteners 126.

The weight 116 also includes a dome portion 128 operable to be engagedby a spring biased piston lock 130 movable in the stepped bore 132 inthe housing 68. The piston 130 is movable in the bore 132, in responseto pressure fluid being admitted to the interior 96, against the bias ofthe spring 134 to allow the weight 116 to be free to tilt with respectto the centerline 136 about the spherical pedestal 118. The centerline136 passes through the intersection of the centerlines 106 and 108 andis perpendicular to the centerlines 106 and 108. The piston 130 includesan O-ring 138 forming a seal between the piston and the bore 132. Inresponse to pressure fluid acting on the face 140, the piston is movableupward in the bore 132 until the O-ring 138 passes the lower edge of theV-shaped notches 142, FIG. 1 1, allowing pressure fluid to vent from theinterior 96 through clearance provided between the piston 130 and thebore 132 and out through the notches 142. The spring 134 is of apredetermined size to permit the piston to move upward a sufficientamount to release its holding force on the weight 116 and allow theescape of pressure fluid from the interior 96. Pressure fluid issupplied to the interior of the housing 68 through conduits 1440, 144b,1440, and 144d in com munication with the valves 144a, 144b, 1440, and14411, respectively.

The weight 116 is retained in the position shown in FIG. 7 by the pistonlock 130 to prevent unwanted movement of the weight when the directionsensing unit 66 is not in use. With pressure fluid supplied through theconduits to the passages 115 in the valve seats 110, the ball valveelements will be raised off the seats to engage the surface 146 on theweight and allow the flow of pressure fluid into the interior 96.Pressure fluid acting on the piston 130 will cause the piston to moveupward unlocking the weight 116. When the direction sensing unit isoriented such that the resultant force of gravity on the weight 116 actsalong the centerline 136, which comprises a reference axis for aligningthe sensing unit so that the centerline 136 is coincident with a plumbline, the weight will be balanced to remain in the position shown inFIG. 7. However, if the sensing unit is tilted in any direction theresultant force of gravity on the weight will cause the weight to tiltto engage one or possibly two adjacent ball valves forcing the valvesagainst their respective seats and closing off the flow of pressurefluid through the respective passages. The shutoff of fluid flowproduces a signal in the form of a pressure increase in the respectiveconduits leading to the closed valves. This pressure increase is used asa control signal to effect the positioning of the feed support 42 toassume a predetermined direction in accordance with the operation of thecontrol system of the present invention. A small passage 149 is providedin the housing 68 to vent pressure fluid trapped in the interior 96.

The control system of the present invention includes a pressure fluidcontrol circuit illustrated schematically in FIG. 9 substantially inaccordance with USA. Standard fluid power symbols. The control circuitof FIG. 9 includes a pressure fluid supply line 150, preferably usingcompressed air as the pressure fluid, having a shutoff valve 152interposed therein. The supply line is connected to each of the conduits144a, 144b, 1440, and 144d for supplying pressure fluid to therespective valves 114a, 114b, 114C, and 114d. Flow restrictors 154 areprovided for limiting the flow of fluid to each valve. The controlsystem also includes a hydraulic control circuit including thepositioning motor 36 having conduits 156 and 158 leading to oppositeends thereof and the positioning motor 48 having conduits 160 and 162leading to its opposite ends. The conduits leading to the positioningmotors 36 and 48 are operable to be connected to a source of hydraulicpressure fluid such as the pump 164 and to a reservoir 166 depending onthe position of control valves 168 and 170 interposed in the circuit.The control valves 168 and 170 represented schematically in FIG. 9 areof a type which may be actuated by pressure fluid or manually topositions a and b and are normally in the blocked position 0 in responseto balanced actuating forces or no actuating force. As shown in FIG. 9valves 114a and 114b are respectively connected to the position a and bactuators of control valve 168 for controlling the operation ofpositioning motor 48 and valves 114d and 114C are respectively connectedto the position a and b actuators of control valve 170 for controllingthe operation of positioning motor 36. The control valves 168 and 170and the control circuit shutoff valve 152 may be suitably located on thefeed support 42 or at an operator control station on the undercarriage12.

The control circuit of FIG. 9 is operable to actuate the positioningmotors 36 and 48 to position the feed support 42 so that the drill rodaxis 62 assumes a predetermined attitude or direction. With pressurefluid supplied to the conduits 144a, 144b, 1440, and 144d, the valves114a, 114b, 1140, and 114d will allow fluid to flow into the interior 96of the housing 68 to actuate the piston lock 130 to release the weight116 to be free to tilt about the spherical pedestal base 118. If thesensing unit is positioned such that the force of gravity acting on theweight 116 is substantially along the centerline 136 the weight willremain in the position of FIG. 7 and all of the ball valves will beopen. The flow restrictors 154 will provide for a uniform reducedpressure in all conduits and with equal pressure on the position a and bactuators of control valves 168 and 170 these valves will remain closedor in position 0.

If the direction of the gravitational force acting on the weight 116should change due to movement of the feed support 42, upon which thesensing unit 66 is mounted, the weight would tilt to engage one of theball valve elements 114a, 114b, 114C or 114d to block the flow ofpressure fluid through its associated conduit. A

pressure increase in that conduit would result in the actuation of theassociated control valve actuator causing one of the control valves 168or 170 to valve pressure fluid to the respective positioning motors 48or 36 thereby effecting positioning of the feed support 42. It ispossible that the change in position of the feed support 42 could causethe weight 116 to tilt to engage a combination of one of the valves 1140or 114b on the centerline 108 and one of the valves 1140 or 114d on thecenterline 106 simultaneously, in which case both control valves 168 and170 would be actuated to supply pressure fluid to the positioning motors48 and 36 simultaneously. The surface 120 on the pedestal 118 providesfor reduced tendency of the weight to tilt when minor deviations fromthe true vertical orientation of the centerline 136 are encountered.This does not affect the accuracy of the sensing unit for mostapplications including the primary uses of the drill rig disclosed.

By way of example of the operation of the control system of the presentinvention the position of the sensing unit 66 in the mounting bracket 72on the feed support 42 may be assumed to be that shown in FIG. 3. If thefeed support 42 should be swung out of the vertical as indicated by thedotted line position of FIG. 9 the weight 116 would tilt to engage andclosed ball valve 114a thereby causing a pressure increase in conduit144a and actuation of control valve 168 to position a. In position acontrol valve 168 would supply pressure fluid to the rod end ofpositioning motor 48 causing the feed support to swing about the pivotaxis 46 back to a substantially vertical position whereupon thegravitational force acting on weight 116 would cause the weight toresume the position of FIG. 7 allowing ball valve 1140 to open reducingthe pressure in conduit 144a and resulting in control valve 168 shiftingto the blocked position 0. If the feed support 42 were to be swung aboutthe axis 46 in the opposite direction, the weight 116 would tilt toclose valve 1l4b and thereby effect the shifting of control valve 168 toposition b to valve pressure fluid to the opposite end of positioningmotor 48 until the feed support was again vertical.

In a similar manner if the feed support were pivoted about thepositioner pivot axis 38 in one direction or the other, commencement ofoperation of the control system would result in the weight 116 tiltingto engage either ball valve l 140 or 114d which would result in theshifting of the control valve 170 to position b or a. This would resultin the actuation of the positioning motor 36 to extend or retract itspiston rod pivoting the feed support back to the vertical position.

As previously mentioned a desired use of the directional control systemof the present invention is to provide for drilling a series of spacedparallel blast holes for presplitting a rock face. FIG. 6 illustrates aschematic cross section of a road right of way 172 comprising thesloping sides 174 and 176 to be formed through the hill 178. Thepresplit holes 180, FIG. 5, are drilled along the intersection 182 ofthe plane of the slope 176 with the surface of the hill 178 and aredesired to be parallel. The undercarriage 12 is desirably positioned asshown in FIG. with respect to the intersection line 182 and the feedsupport 42 is positioned so that the drill rod axis 62 is in the planeof the slope 176. The alignment of the drill rod may be initially set byconventional methods such as with the use of a level protractor orclinometer. The feed support 42 is initially positioned to provide thedesired angle of the drill rod axis 62 with respect to the vertical or aplumb line 64, FIG. 1, by manually actuating the control valves 168 andto operate the respective positioning motors 48 and 36.

When the desired direction of the drill rod axis 62 has beenpredetermined by positioning the feed support 42 the sensing unit 66 ispositioned so that the centerline 136, FIG. 7, is coincident with aplumb line. This may be accomplished by releasing the clamping plate 76and aligning the tubular extension 102 with a suitable indicator such asa clinometer or a plumb line attached to the bracket 72. The pivotedbracket 72 is also aligned so that the centerline 108 of the sensingunit 66 is parallel to the intersection line 182, and therefore also theplane of the slope 176, by actuating the valve 94 to move the cylinder80. With the sensing unit 66 properly set to have the centerline 136coincident with a vertical or plumb line, when it is desired to move thefeed support from the center position shown in FIG. 5 to drill theadditional holes along the line 182, the control valves 168 and 170 aremanually actuated along with suitable controls for swinging andextending the telescoping boom portion 30 until the feed support 42 isin the approximate location and attitude for drilling. The sensing unit66 is then actuated by opening valve 152. If the sensing unit is not inan attitude which places the centerline 136 coincident with thevertical, the weight 116 will tilt to actuate the control circuit asaforedescribed until the positioning motors 36 and 48 have oriented thesensing unit 66 so that the centerline 136 is vertical. Operation of thepositioning motors by manually overriding the automatic actuation of thecontrol valves 168 and 170 may be necessary until the bit 58 is spottedover the exact desired hole location. However, the final directionalattitude of the feed support to place the drill rod axis 62 in thepredetermined direction is assured with the control system disclosedherein. Furthermore, the accuracy of the directional attitude of thefeed support for all of the holes 180 enables the drilling of deeperholes and hence the presplitting of deeper cuts without the danger offaulty cleavages or fissures developing in the rock face.

As described in the foregoing paragraphs the sensing unit 66 is alignedso that the centerline 108 is parallel to the intersection line 182 andthe plane of the slope 176. This alignment is maintained with sufficientaccuracy by the pressure fluid circuit including the cylinders 80 and 84as the boom is pivoted about the axis 22 and is necessary to assureproper positioning of the feed support by the positioning motor 48.Moreover, in order that the ball valves 114a, 114b, 1140 and 114dmaintain their proper orientation with respect to the feed support 42 itis necessary to prevent rotation of the sensing unit 66 about the axisor centerline 136. To this end, referring to FIGS. 3 and 4, a slot 186is formed on the periphery of the housing 68 in a plane through thecenterline 136. A cylindrical pin 188 mounted on the bracket portion 72projects into the slot 186 in a plane perpendicular to the centerline 36and through the center of the spherical housing 68. The arrangement ofthe pin 188 and slot 186 provides for movement of the sensing unit inany direction within the envelope of a conical surface of revolutionabout the centerline 136 as shown in FIG. 3 by the dotted line positionsof the tubular extension 102.

It is also not necessary that the rig undercarriage 12 be positionedwith respect to the intersection line 182 as illustrated in FIG. toenable the drilling of a series of substantially parallel and coplanarholes. By providing the control valve 94 in the servo circuit 86, 88 thebracket portion 72 may be aligned parallel to the intersection line 182even though the undercarriage is not oriented as shown in FIG. 5. Someerror in the positioning of the bracket 72 in response to pivoting ofthe boom 18 will be introduced due to the fact that equal linearmovement of the piston rods of the cylinders 84 and 80 may not produceequal angular movement of the boom 18 and the bracket portion 72, eachwith respect to their own pivot axes. However, such errors are of noconsequence within the limits of angular movement of the boom 18 aboutthe axis 22 for conventional drill rigs.

It may be appreciated from the foregoing that the directional controlsystem of the present invention may be used to substantially improve thespeed and accuracy of drilling a plurality of blast holes not only forpresplit or preshearing work but for tunnel face drilling and room andpillar mine excavation as well. Furthermore, the directional controlsystem of the present invention may be advantageously used withvirtually any type of drilling apparatus havlng a feed support operableto be pivotally moved about two axes perpendicular to one another.

What is claimed is:

1. In a rock drill apparatus:

a movable support;

an elongated drill feed support;

pivotal connection means between said feed support and said movablesupport providing for movement of said feed support with respect to saidmovable support; drill motor means including elongated drill rod meanshaving a longitudinal axis, said drill motor means being mounted on saidfeed support and operable to be reversibly driven therealong;

pressure fluid actuated positioning motor means operably connected tosaid movable support and said feed support for moving said feed supportwith respect to said movable support; and,

control means including a direction sensing unit mounted on said feedsupport for movement therewith and characterized by a weight mounted onsaid sensing unit for movement with respect to said sensing unit inresponse to gravitational force acting on said weight, a pressure fluidcontrol circuit for producing pressure fluid signals in response tomovement of said weight with respect to said sensing unit, a pressurefluid control circuit including control valves interposed therein andresponsive to receiving pressure fluid signals from said first mentionedcontrol circuit for valving pressure fluid to said positioning motormeans to move said feed support to maintain said drill rod axis in apredetermined directional attitude in response to movement of saidmovable support, and fluid operated locking means on said sensing unitfor locking said weight to prevent movement of said weight with respectto said sensing unit.

2. In a rock drill apparatus:

a movable support;

an elongated drill feed support;

pivotal connection means between said feed support and said movablesupport providing for movement of said feed support with respect to saidmovable support about first and second pivot axes;

drill motor means including elongated drill rod means having alongitudinal axis, said drill motor means being mounted on said feedsupport and operable to be reversibly driven therealong;

pressure fluid actuated positioning motor means operably connected tosaid movable support and said feed support for moving said feed supportwith respect to said movable support about said first and second pivotaxes; and,

control means including a direction sensing unit mounted on said feedsupport for movement therewith and characterized by a weight mounted onsaid sensing unit for movement with respect to said sensing unit inresponse to gravitational force acting on said weight, signal producingmeans for producing signals in response to the movement of said weightwith respect to said sensing unit, and a pressure fluid control circuitincluding control valves interposed therein and responsive to receivingsignals from said signal producing means for valving pressure fluid tosaid positioning motor means to move said feed support about said firstand second pivot axes to maintain said drill rod axis in a predetermineddirectional attitude.

3. The invention set forth in claim 2 wherein:

said first pivot axis is substantially perpendicular to said secondpivot axis and said control means is operable to actuate saidpositioning motor means to pivot said feed support about said first andsecond pivot axes simultaneously.

4. The invention set forth in claim 2 wherein:

said signal producing means comprises a pressure fluid control circuitincluding a plurality of pressure fluid valves mounted on said sensingunit and operable to be engaged with and actuated by said weight inresponse to the movement of said weight to produce a pressure fluidsignal for operating said control valves.

5. The invention set forth in claim 4 wherein:

said plurality of valves operable to be engaged by said weight includesat least two valves arranged along a first centerline and at least twovalves arranged along a second centerline perpendicular to said firstcenterline, and said weight is located on said sensing unit with respectto a reference axis substantially perpendicular to said first and secondcenterlines whereby when said drill rod axis is positioned in saidpredetermined directional attitude the direction of a resultantgravitational force acting on said weight is substantially coincidentwith said reference axis.

6. The invention set forth in claim 5 wherein:

said feed support includes a mounting bracket for mounting said sensingunit in a plurality of positions whereby said reference axis may bepositioned in a predetermined direction with respect to said drill rodaxis.

unit is operable to position said sensing unit to maintain one of saidcenterlines in a plane substantially parallel to a plane through saiddrill rod axis. 9. The invention set forth in claim 2 wherein: saidpositioning motor means includes a first pressure fluid actuatedpositioning motor for pivoting said feed support about said first pivotaxis and a second pressure fluid actuated positioning motor for pivotingsaid feed support about said second pivot axis.

1. In a rock drill apparatus: a movable support; an elongated drill feedsupport; pivotal connection means between said feed support and saidmovable support providing for movement of said feed support with respectto said movable support; drill motor means including elongated drill rodmeans having a longitudinal axis, said drill motor means being mountedon said feed support and operable to be reversibly driven therealong;pressure fluid actuated positioning motor means operably connected tosaid movable support and said feed support for moving said feed supportwith respect to said movable support; and, control means including adirection sensing unit mounted on said feed support for movementtherewith and characterized by a weight mounted on said sensing unit formovement with respect to said sensing unit in response to gravitationalforce acting on said weight, a pressure fluid control circuit forproducing pressure fluid signals in response to movement of said weightwith respect to said sensing unit, a pressure fluid control circuitincluding control valves interposed therein and responsive to receivingpressure fluid signals from said first mentioned control circuit forvalving pressure fluid to said positioning motor means to move said feedsupport to maintain said drill rod axis in a predetermined directionalattitude in response to movement of said movable support, and fluidoperated locking means on said sensing unit for locking said weight toprevent movement of said weight with respect to said sensing unit.
 2. Ina rock drill apparatus: a movable support; an elongated drill feedsupport; pivotal connection means between said feed support and saidmovable support providing for movement of said feed support with respectto said movable support about first and seconD pivot axes; drill motormeans including elongated drill rod means having a longitudinal axis,said drill motor means being mounted on said feed support and operableto be reversibly driven therealong; pressure fluid actuated positioningmotor means operably connected to said movable support and said feedsupport for moving said feed support with respect to said movablesupport about said first and second pivot axes; and, control meansincluding a direction sensing unit mounted on said feed support formovement therewith and characterized by a weight mounted on said sensingunit for movement with respect to said sensing unit in response togravitational force acting on said weight, signal producing means forproducing signals in response to the movement of said weight withrespect to said sensing unit, and a pressure fluid control circuitincluding control valves interposed therein and responsive to receivingsignals from said signal producing means for valving pressure fluid tosaid positioning motor means to move said feed support about said firstand second pivot axes to maintain said drill rod axis in a predetermineddirectional attitude.
 3. The invention set forth in claim 2 wherein:said first pivot axis is substantially perpendicular to said secondpivot axis and said control means is operable to actuate saidpositioning motor means to pivot said feed support about said first andsecond pivot axes simultaneously.
 4. The invention set forth in claim 2wherein: said signal producing means comprises a pressure fluid controlcircuit including a plurality of pressure fluid valves mounted on saidsensing unit and operable to be engaged with and actuated by said weightin response to the movement of said weight to produce a pressure fluidsignal for operating said control valves.
 5. The invention set forth inclaim 4 wherein: said plurality of valves operable to be engaged by saidweight includes at least two valves arranged along a first centerlineand at least two valves arranged along a second centerline perpendicularto said first centerline, and said weight is located on said sensingunit with respect to a reference axis substantially perpendicular tosaid first and second centerlines whereby when said drill rod axis ispositioned in said predetermined directional attitude the direction of aresultant gravitational force acting on said weight is substantiallycoincident with said reference axis.
 6. The invention set forth in claim5 wherein: said feed support includes a mounting bracket for mountingsaid sensing unit in a plurality of positions whereby said referenceaxis may be positioned in a predetermined direction with respect to saiddrill rod axis.
 7. The invention set forth in claim 6 wherein: said rockdrill apparatus includes a frame, said movable support being pivotallymounted on said frame; said mounting bracket for said sensing unit ispivotally mounted on said feed support; and, said rock drill apparatusincludes means for controlling the position of said sensing unit inresponse to pivotal movement of said movable support with respect tosaid frame.
 8. The invention set forth in claim 7 wherein: said meansfor controlling the position of said sensing unit is operable toposition said sensing unit to maintain one of said centerlines in aplane substantially parallel to a plane through said drill rod axis. 9.The invention set forth in claim 2 wherein: said positioning motor meansincludes a first pressure fluid actuated positioning motor for pivotingsaid feed support about said first pivot axis and a second pressurefluid actuated positioning motor for pivoting said feed support aboutsaid second pivot axis.